PROJECT SUMMARY/ABSTRACT: My long-term career goal is to become a leading clinician-scientist in the field of cerebral aneurysm research. I have had a long commitment to biomedical research since an undergraduate at Stanford University working in the laboratory of Dr. Edward Mocarksi on a project studying regulation of the B2.7 promoter of human cytomegalovirus. As a medical student at Columbia University I worked under Dr. Saul Silverstein mapping functional domains of the IE0 gene of herpes simplex virus. I then worked under Dr. E. Sander Connolly and Dr. David Pinsky studying pathophysiologic mechanisms of stroke in a mouse model. As a resident and fellow at the Massachusetts General Hospital, I worked in the laboratory of Dr. Joseph Vacanti on a project seeding polymers with endothelial cells to create a vascular graft for treating cerebral aneurysms. My immediate objective for the next five years is to become an independent investigator. I will start a rigorous didactic program focused on gaining the knowledge and skills necessary to achieve this objective. Scientific skills I will acquire during the award period, include animal surgery, histology, immunohistochemistry, intravital microscopy, stem cell biology techniques, and advanced statistical analysis of data. To complement my laboratory experience, I will take graduate coursework in the University of Florida Interdisciplinary Program in Biomedical Sciences. I have developed a comprehensive career development program which includes laboratory training, close mentorship, graduate level coursework, research conferences, and oral presentations. My goal is to obtain an NIH R01 award by the time the award finishes. Environment: I will be working in the laboratory of Dr. Edward Scott, an outstanding mentor, who has successfully trained several clinician-scientists and previous recipients of the K08 award. I will have as a consultant, Dr. Christopher Batich in the Department of Materials Science and Engineering, a superb collaborator. I will be working in an outstanding scientific and creative environment with collaborators in the Program in Stem Cell Biology and Regenerative Medicine, the McKnight Brain Institute, and the Department of Materials Science and Engineering to guide my research progress. I have the full committed support of my chairman, the Department of Neurological Surgery, and the University of Florida to devote at least 50% of my time and effort to my research career development. All of the components are in-place to promote a successful outcome in my research proposal and my overall research career development. Research Plan: The long-term goal of this project is to better define the pathophysiology of cerebral aneurysm formation, and, thereby, develop a translational therapy that would treat cerebral aneurysms. The overall objective is to answer the fundamental gap in knowledge of whether inflammation causes cerebral aneurysm formation, or is an epiphenomenon;identifying signaling mechanisms which could be targets for modulation of the aneurysm inflammatory response;and identifying vascular repair cells that can repair the degenerative mechanisms of vascular inflammation. The central hypothesis is that: Cerebral aneurysm formation is an inflammatory process. Modulating the inflammatory response would alter the development of cerebral aneurysms. Vascular repair cells can be identified that repair the degenerative mechanisms caused by vascular inflammation. The rationale for the proposed research is that because cerebral aneurysms can be diagnosed before they rupture, a therapy that would repair the aneurysm inflammatory process and prevent aneurysms from progressing to rupture, would have a significant beneficial impact for the public health. Guided by strong preliminary data, this hypothesis will be tested by pursuing three specific aims: 1) Demonstrate that cerebral aneurysm formation is caused by an inflammatory process;2) Identify signaling mechanisms involved in the inflammatory process as targets for modulation to alter the development of aneurysms;and 3) Identify vascular repair cells that repair the degenerative mechanisms caused by vascular inflammation. Under the first aim, two lines of experiments will be performed: 1) aneurysms will be produced in mice by activating inflammation (injecting activated macrophages and neutrophils into normal mouse carotid artery);and 2) performing an elastase saccular aneurysm model in immune-deficient mice that can not mount an inflammatory response. Under the second aim, signaling mechanisms at each step of the leukocyte recruitment cascade: 1) chemotaxis, 2) rolling, 3) adhesion, 4) transmigration;will be blocked in an elastase saccular aneurysm model. Under the third aim, cell-specific populations of CD133+ endothelial progenitor cells (EPCs), hematopoietic stem cells, and mesenchymal stem cells will be seeded into Matrigel and other polymers developed by our collaborator, Dr. Christopher Batich, and injected into murine elastase saccular aneurysms which will later be evaluated for evidence of re-endothelialization and inhibition of the vascular inflammatory response. PUBLIC HEALTH RELEVANCE: PROJECT NARRATIVE: The proposed studies are of an important and under-investigated area of cerebral aneurysm pathophysiology that would directly translate into therapies that could treat cerebral aneurysms, such as 1) endovascular devices carrying signaling mechanisms that reverse the degenerative inflammatory process and promote vascular repair, and 2) medical drug therapies that arrest the degenerative inflammatory process and stabilize aneurysms from growing and progressing to rupture. The proposed research has relevance to the public health and the Nation's economic well-being because there is a significant incidence of cerebral aneurysms in the population, 3.6-6.0%;cerebral aneurysms are associated with significant morbidity and mortality;and the costs of subarachnoid hemorrhage in the United States are enormous ($5.6 billion/year).